Attempts are being made to isolate microsomal lipids, to form liposomes from these and reincorporate specifically purified enzymes to simplify the task of determining the interaction between microsomal enzymes and how substrates affect this interaction. With cytochrome P-450, the spin state equilibrium between high and low spin as affected by phospholipid and specific enzymes will be determined, and attempts will be made to relate this to the oxidation reduction potential or extent of interaction of the proteins.